I guess it depends on what level of gigs one is used to, but there's merit on many levels.
Like Andy said, being able to make them sound as good as possible is a very good lesson.
House kits is the name of the game in som many situations and no, it's not really an option to bring your full kit for a multitude of reasons,. Flying in, there's no time, the venue wants you to use the house kit, and really, if it's a small thing where you're just helping out a bit it's not worth it.
There's also the type of bar where you just really don't want to bring your nicest gear.
Why would you then also have a nice kit.? It's not like it won't get used. Both for home, recording and when you play stages where music is the main thing and there will be no beer spilled on it. A real stage, basically.
I can very much relate to the New York thing the 80/20 guy talks about because all these small venue semi-acoustic gigs also really call for something different. Not necessarily a cajon kit, but something of that ilk. Something that just fits the vibe and works for that situation. All these little gadgets you can use to get different sounds, different utensils, all sorts of stacks and dampening etc.. are all very useful and they also add a bit of charm. Bringing the real kit? What is a real kit?